Radiative lifetimes of NO A Σ2+(v′=,1,2) and the electronic transition moment of the A Σ2+−X Π2 system

Abstract

Improved measurements of the radiative lifetimes of NO A Σ2+(v′=0,1,2) are presented and used to update the absolute electronic transition moment for the NO γ bands. The pressure-dependent fluorescence decay rate was measured in a low-pressure, room-temperature, flow cell containing dilute mixtures of NO in N2 using time-resolved laser-induced fluorescence excited with a picosecond laser and detected with a microchannel-plate photomultiplier tube. Fluorescence decay rates were determined using an analysis procedure that accounted for the electronic response of the detection system and measurement noise. Radiative lifetimes were determined from an extrapolation of the measured decay rates to zero pressure. In comparison with prior measurements of these radiative lifetimes, the improved experimental approach and analysis procedure result in a significant improvement in the measurement precision. The accuracy of the fluorescence decay-rate measurements was confirmed by independent measurements using time-correlated single-photon counting and time-resolved probing of laser-excited population in A Σ2+ using 266 nm photoionization and charge detection. The measured radiative lifetimes are 192.6±0.2 ns for v′=0, 186.2±0.4 ns for v′=1, and 179.4±0.7 ns for v′=2. The measured lifetimes are shown to be in outstanding agreement with those predicted by an electronic transition moment that is identical in form to the function recommended by Luque and Crosley [J. Chem. Phys. 111, 7405 (1999)] after appropriate rescaling. This rescaling does not affect the agreement of the transition moment function with the previously reported vibrational branching ratios and improves agreement with previously reported absolute oscillator strength measurements. Based on the rescaled transition moment, updated values of absolute transition probabilities in the NO A Σ2+−X Π2 system are presented.

Collisions of electronically excited molecules: differential cross-sections for rotationally inelastic scattering of NO(A2Σ+) with Ar and He

“…Briefly, the first laser excites NO molecules from the v ¼ 0, J ¼ 0.5 level of the X 2 Å 1/2 ground state to the v ¼ 0, N ¼ 0, J ¼ 0.5 level of the A 2 AE þ state via the Q 1 (0.5) transition at $226 nm in the beam intersection region of the crossed molecular/ atomic beam machine. The molecules are then given 400 ns (approximately twice the radiative lifetime of the NO(A 2 AE þ ) state [35]) to collide, after time which the final rotational state (N 0 ) and velocities of the products of rotationally inelastic NO(A 2 AE þ ) þ Ar and NO(A 2 AE þ ) þ He collisions are probed using a [1 þ 1 0 ] REMPI and VMII detection scheme. In the 400 ns between excitation and detection the molecules move only a few hundred microns, and thus the electronically excited NO(A 2 AE þ ) remains within the probe beam volume, and those that have not fluoresced are detected.…”

Transient Mixing Enhancement of a Transverse Jet in Supersonic Cross Flow Using Pulse Detonation

“…The total fluorescence decay r the fluorescence natural decay rate, A, and the electro s evaluated using the Settersten database. [29][30][31] Lastly, f he probed ro-vibronic state, which was calculated using s ions [32] for the specific spin-split J state of NO probed vel of X ed and computed NO PLIF as the PD plume evolved downstre agreeing reasonably well with the NO PLIF, the CFD so he relative differences between the NO jet plume with on. Figure 9 shows the comparison between the NO e PD interaction.…”

Communication: Direct angle-resolved measurements of collision dynamics with electronically excited molecules: NO(A2Σ+) + Ar

“…The molecules are then given 400 ns [approximately twice the radiative lifetime of NO(A) (Ref. 14)] to collide (center of mass collision energy 1855 ± 180 cm −1 ), after which the products of rotationally inelastic NO(A) + Ar collisions are probed using a [1 + 1 ] REMPI detection scheme. In the first step of the detection scheme, a Nd:YAGpumped dye laser (Rhodamine B dye, ∼600 nm, ∼0.03 cm −1 resolution), excites NO(A) molecules to the E 2 + state via the R(N ) branch of the E 2 + ← A 2 + (0,0) band.…”